System and method for dynamically measuring blade position during flight of rotorcraft

Abstract

To provide a system and method for dynamically measuring blade position during flight of a rotorcraft.SOLUTION: A blade 14 of a rotorcraft 10 is repeatedly illuminated by a light source during flight of the rotorcraft 10 while the blade is rotating. The method also includes a step of detecting radiation scattered from the blade in response to illumination of the blade 14. The method further includes a step of determining at least one of a blade pitch angle (ΔθP), a blade flap angle (ΔθF), a blade leading position or a blade lagging position on the basis of the radiation that is scattered from the blade 14 and detected. A rotorcraft 10 is also provided that includes a chip-scale light detection and ranging (LIDAR) sensor configured to illuminate a plurality of blades 14 while the blades 14 are rotating in order to permit blade 14 position to be measured or to illuminate terrain beneath the rotorcraft 10 in order to perform an altitude measurement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Systems and methods are provided for measuring blade position of a rotorcraft, and more particularly for dynamically measuring blade position during flight of the rotorcraft. [Background technology]

[0002] Rotary-wing aircraft, such as helicopters, include multiple blades that rotate to provide lift during flight. Rotary-wing aircraft generally provide a relatively smooth flight when the blades maintain predetermined blade positions, e.g., blade pitch angle, blade flap angle, and blade advanced or retarded positions. However, sometimes the blade positions may vary from the desired blade positions, such as by having different blade pitch angles, different blade flap angles, and / or being positioned in advanced or retarded positions. In these cases, the flight of the rotorcraft often becomes less smooth, potentially reducing the flight experience of the crew or passengers and / or causing problems for cargo carried by the rotorcraft.

[0003] In these instances where blade position has changed, the rotorcraft blades cannot be repositioned to return to the predetermined blade position at least until the rotorcraft completes its flight. In some cases, the rotorcraft blades cannot be repositioned even after the flight is completed, and instead must wait for the rotorcraft to return to a maintenance depot or other facility that can perform such repairs. As such, potentially rougher flight conditions caused by blade position variations may not be addressed as quickly as desired. Summary of the Invention [Means for solving the problem]

[0004] A blade positioning system and method are provided in accordance with exemplary embodiments for dynamically measuring blade positions during rotorcraft flight. Based on the dynamically corrected blade positions, the rotorcraft of the exemplary embodiments may be configured to correct the blade positions during the rotorcraft's flight. As a result, the dynamic measurement of blade positions, and in some embodiments, the in-flight correction of blade positions, may allow the rotorcraft to return to smoother flight conditions in a more expeditious manner, such as during the flight itself, without waiting for the completion of the flight and / or the rotorcraft's return to a maintenance depot or other repair facility. The blade positioning system and method of the exemplary embodiments utilize track sensors, such as chip-scale light detection and ranging (LIDAR) sensors, carried by the rotorcraft fuselage so as not to appreciably increase the rotorcraft's size and weight. While chip-scale LIDAR sensors may be utilized to measure blade positions, another exemplary embodiment of the rotorcraft may utilize chip-scale LIDAR sensors as altimeters, such as to facilitate landing of the rotorcraft.

[0005] In an exemplary embodiment, a method is provided for dynamically measuring blade position during flight of a rotorcraft. The method includes repeatedly illuminating blades of the rotorcraft with coherent light during flight of the rotorcraft while the blades are rotating. The method also includes detecting radiation scattered from the blades in response to illuminating the blades. The method further includes determining at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on the detected radiation scattered from the blades.

[0006] In an exemplary embodiment, a method repeatedly illuminates a rotorcraft blade at a location closer to the distal end of the blade than the rotor mast about which the blade rotates. In an exemplary embodiment, the method repeatedly illuminates the blade with a plurality of track sensors positioned at different locations on the rotorcraft fuselage.

[0007] In an exemplary embodiment, the method determines the blade pitch angle by determining the range to the blade based on the detected radiation scattered from the blade, and then determining the blade pitch angle based on the width of the blade and the deviation of the range to the blade from the range to a reference blade position with no pitch. In this exemplary embodiment, in which the blade is repeatedly illuminated by radiation generated by a laser source, the method determines the range to the blade by determining the range between the laser source and the edge of the blade.

[0008] In an exemplary embodiment, the method determines a blade flap angle by determining a range to the blade based on detected radiation scattered from the blade, and then determining a blade flap angle based on the blade length and the deviation of the range to the blade from the range to a reference blade position without the flap. In another exemplary embodiment, the method determines a leading or lagging blade position by detecting the presence of the blade at a predetermined position in the blade's rotational path and determining a detection time at which the presence of the blade is detected. The method of this exemplary embodiment then determines a blade position based on a relationship between the detection time and a predetermined time associated with a reference blade that is neither leading nor lagging. In this regard, the method determines a blade position by determining a leading blade position if the detection time precedes the predetermined time, and determining a lagging blade position if the detection time lags the predetermined time.

[0009] In another exemplary embodiment, a blade positioning system for dynamically measuring blade position during flight of a rotorcraft is provided. The blade positioning system includes a track sensor mounted to the rotorcraft. The track sensor includes a laser source configured to repeatedly illuminate blades of the rotorcraft with coherent light during flight of the rotorcraft while the blades are rotating. The track sensor also includes at least one photodetector configured to detect radiation scattered from the blades in response to the illumination of the blades. The system of this exemplary embodiment also includes processing circuitry configured to determine at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on the radiation scattered from the blades and detected by the at least one photodetector in response to the track sensor.

[0010] The track sensor of the exemplary embodiment is mounted on the rotorcraft such that the light source is configured to repeatedly illuminate the blade at a location closer to the distal end of the blade than the rotor mast about which the blade rotates. In the exemplary embodiment, the blade positioning system also includes a plurality of track sensors mounted at different locations on the rotorcraft.

[0011] The processing circuitry of the exemplary embodiment is configured to determine the blade pitch angle by determining the range to the blade based on the detected radiation scattered from the blade, and determining the blade pitch angle based on the width of the blade and the deviation of the range to the blade from the range to a reference blade position with no pitch. The processing circuitry of this exemplary embodiment is configured to determine the range by determining the range between the laser source and the edge of the blade.

[0012] The processing circuitry of the exemplary embodiment is configured to determine the blade flap angle by determining a range to the blade based on the detected radiation scattered from the blade, and to determine the blade flap angle based on the length of the blade and the deviation of the range to the blade from the range to a reference blade position without the flap. In another exemplary embodiment, the track sensor is configured to detect the presence of the blade at a predetermined position in the rotational path of the blade, and the processing circuitry is configured to determine a detection time at which the presence of the blade is detected. In this exemplary embodiment, the processing circuitry is configured to determine the blade position based on a relationship between the detection time and a predetermined time associated with a reference blade that is neither leading nor lagging. The processing circuitry of this exemplary embodiment is configured to determine the blade position by determining a leading blade position if the detection time leads the predetermined time, and determining a lagging blade position if the detection lags the predetermined time.

[0013] In a further exemplary embodiment, a rotorcraft is provided that includes a fuselage, a plurality of blades configured to rotate relative to the fuselage, and a chip-scale light detection and ranging (LIDAR) sensor carried by the fuselage. The chip-scale LIDAR sensor includes a laser source configured to provide illumination with coherent light during flight of the rotorcraft, and at least one photodetector configured to detect scattered radiation in response to the illumination provided by the laser source. The chip-scale LIDAR sensor is carried by the fuselage such that the laser source is configured to illuminate the plurality of blades while they are rotating to enable measurement of blade positions or to illuminate terrain below the rotorcraft to provide altitude measurements.

[0014] The laser source of the exemplary embodiment includes a frequency-modulated continuous wave laser diode. The at least one photodetector of the exemplary embodiment includes a pair of dual balanced photodetectors. The chip-scale LIDAR sensor of the exemplary embodiment also includes a splitter configured to split light generated by the laser source into first and second portions, the first portion being directed to illuminate the plurality of blades while the blades are rotating or to illuminate the terrain below the rotorcraft. The chip-scale LIDAR sensor of the exemplary embodiment also includes a waveguide configured to support propagation of the second portion of the light generated by the laser source, and a coupler configured to combine the second portion of the light propagating along the waveguide with radiation scattered in response to the illumination provided by the laser source. The at least one photodetector of the exemplary embodiment is responsive to the coupler and configured to receive the second portion of the light propagating along the waveguide as well as the radiation scattered in response to the illumination provided by the laser source.

[0015] The rotorcraft of this exemplary embodiment also includes a processing circuit configured to, in response to the chip-scale LIDAR sensor, determine at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on radiation scattered from each blade of the plurality of blades and detected by the at least one photodetector. The rotorcraft of this embodiment also includes an actuator configured, in response to the processing circuit, to modify a position of each blade during flight based on the at least one of the blade pitch angle, the blade flap angle, the blade lead position, or the blade lag position determined by the processing circuit. Having described certain examples of the present disclosure in general terms above, reference is now made to the accompanying drawings, which are not necessarily drawn to scale. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a perspective view of a rotorcraft having a track sensor, such as a chip-scale light detection and ranging (LIDAR) sensor, carried by the rotorcraft fuselage and configured to repeatedly illuminate the rotorcraft blades during flight, in accordance with an exemplary embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of a chip-scale LIDAR sensor according to an exemplary embodiment of the present disclosure. [Figure 3] FIG. 1 is a block diagram of a blade positioning system including a track sensor, such as a chip-scale LIDAR sensor, according to an exemplary embodiment of the present disclosure. [Figure 4] 4 is a flowchart illustrating operations performed by a blade positioning system such as that of FIG. 3, according to an exemplary embodiment of the present disclosure. [Figure 5] 1 is a top view of a plurality of blades of a rotorcraft and the rotational paths of the blades relative to a plurality of track sensors carried by the rotorcraft, in accordance with an exemplary embodiment of the present disclosure; [Figure 6] 1 is a side view of a distal portion of a rotorcraft blade illustrating the relative position of a track sensor with respect to the blade, in accordance with an exemplary embodiment of the present disclosure; [Figure 7] 7 is another side view of a portion of a blade in transverse cross section taken along line 7-7 of FIG. 5 illustrating determination of blade pitch angle according to an exemplary embodiment of the present disclosure. [Figure 8] 4 is a flowchart illustrating operations performed to determine blade pitch angle according to an exemplary embodiment of the present disclosure. [Figure 9] 9 is another side view of the blade in longitudinal cross section along line 9-9 of FIG. 5 illustrating the determination of blade flap angle according to an exemplary embodiment of the present disclosure. [Figure 10] 4 is a flowchart illustrating operations performed to determine blade flap angle according to an exemplary embodiment of the present disclosure. [Figure 11] 10 is a flowchart illustrating operations performed to determine blade position with respect to lead or lag according to an exemplary embodiment of the present disclosure. [Figure 12] FIG. 1 is a perspective view of a rotorcraft having a chip-scale LIDAR sensor mounted on the underside of the fuselage to provide altitude measurements according to another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] Some examples of the present disclosure are described more fully below with reference to the accompanying drawings, in which some, but not all, examples of the present disclosure are shown. Indeed, the present disclosure may be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these examples are provided to satisfy applicable legal requirements. Like numerals refer to like elements throughout. As used herein, the terms "data," "content," "information," and similar terms may be used interchangeably to refer to data that may be transmitted, received, and / or stored in accordance with examples of the present disclosure. Therefore, use of such terms should not be deemed to limit the spirit and scope of the present disclosure.

[0018] Systems and methods according to example embodiments are provided for dynamically measuring blade position during flight of a rotorcraft. By measuring blade position during flight of the rotorcraft, the rotorcraft of example embodiments may be configured to correct blade position during flight, thereby providing improved flight performance, such as a smoother flight, without waiting for the completion of the flight and / or for the rotorcraft to return to a maintenance depot or other facility equipped to relocate blades.

[0019] Various types of rotorcraft can benefit from dynamic measurement of blade position during flight. By way of example, and not limitation, FIG. 1 illustrates a rotorcraft 10 in the form of a helicopter, which will be referenced throughout to describe systems and methods for dynamically measuring blade position according to exemplary embodiments. As shown, rotorcraft 10 includes a fuselage 12 and a plurality of blades 14 configured to rotate relative to the fuselage. In this exemplary embodiment, rotorcraft 10 includes a rotor mast 16 to which blades 14 are operatively connected and about which the blades are configured to rotate. In the exemplary embodiment illustrated in FIG. 1 , rotorcraft 10 also includes a track sensor 20 mounted to the rotorcraft, and more specifically, mounted to the upper surface 13 of fuselage 12. In this regard, track sensor 20 is mounted to a portion of the upper surface 13 of fuselage 12 within the rotational path of blades 14 such that the blades pass the track sensor during rotation of the blades, such as during flight.

[0020] While the track sensor 20 can be configured in a variety of ways, the track sensor of the exemplary embodiment is a chip-scale laser detection and ranging (LIDAR) sensor. The chip-scale LIDAR sensor can be embodied in an integrated circuit package and, therefore, can add little weight or size to the rotorcraft 10 to which it is attached. While the chip-scale LIDAR sensor can be configured in a variety of ways, as shown in FIG. 2 , the chip-scale LIDAR sensor 21 of the exemplary embodiment includes a laser source 22 configured to generate radiation, e.g., coherent light, directed to illuminate one or more blades 14 of the rotorcraft 10. In the exemplary embodiment, the laser source 22 is a laser diode. The laser diode may be a single-spectral-mode laser diode. In one embodiment, the laser diode is a distributed Bragg reflector (DBR) laser diode or a distributed feedback (DFB) laser diode heterogeneously integrated on an underlying substrate. In the exemplary embodiment, the laser diode is a frequency-modulated continuous wave (FMCW) laser diode to enable FMCW LIDAR operation.

[0021] The chip-scale LIDAR sensor 21 of the embodiment of FIG. 2 also includes at least one photodetector 26, and in the exemplary embodiment, a pair of photodetectors 26a, 26b in a double-balanced configuration. Each of the one or more photodetectors 26 in the exemplary embodiment is a (PIN) photodiode. The photodetector 26 can be monolithically integrated, such as in an embodiment where the photodetector is a germanium (Ge)-on-silicon (Si) photodiode, or heterogeneously integrated with two additional grating couplers that vertically couple the photodetector to an underlying waveguide. To illuminate the blades 14 of the rotorcraft 10 during flight, the chip-scale LIDAR sensor 21 of the illustrated embodiment includes an output coupler 28 (also referred to herein as an outcoupler), such as a transmitted beam grating outcoupler, that receives radiation generated by the laser source 22 and directs light toward the blades 14 of the rotorcraft 10. The light directed by the output coupler 28 toward the blades 14 of the rotorcraft 10 can be collimated, such as by an off-chip collimating lens.

[0022] In the illustrated embodiment, not all of the radiation generated by laser source 22 serves to illuminate blades 14 of rotorcraft 10. Instead, chip-scale LIDAR sensor 21 includes a splitter 30, such as a 1x2 splitter, configured to receive the radiation generated by laser source 22 and split the radiation, such as via output coupler 28, into a first portion 31a that is directed toward and serves to illuminate blades 14 of rotorcraft 10, and a second portion 31b that is directed to at least one photodetector 26a and / or 26b. While splitter 30 may be configured to split the radiation generated by laser source 22 between first portion 31a and second portion 31b in various ratios, the splitter of the exemplary embodiment splits the radiation generated by the laser source such that the first portion that illuminates blades 14 is greater, e.g., in intensity, than the second portion that is directed to at least one photodetector 26. For example, splitter 30 may be configured such that first portion 31a includes 75%-95% of the radiation generated by laser source 22, and in one embodiment, 90%-95% of the radiation generated by the laser source, and second portion 31b includes the remaining radiation, such as 25%-5% of the radiation generated by the laser source, and in one embodiment, 10%-5% of the radiation generated by the laser source. In an exemplary embodiment, splitter 30 may be a directional coupler / splitter or a multi-mode interference (MMI) coupler splitter. Second portion 31b of the radiation may function as a local oscillator (LO) beam.

[0023] In the illustrated embodiment, the chip-scale LIDAR sensor 21 also includes an input coupler 32 (also referred to herein as an in-coupler), such as a receive beam in-coupler. During operation, the input coupler 32 is configured to receive radiation scattered from the blade 14 in response to illumination by light generated by the laser source 22 and then direct the received radiation to at least one photodetector 26 a and / or 26 b. In the illustrated embodiment, the input coupler 32 directs the received radiation to each of a pair of dual balanced photodetectors 26 a and / or 26 b. In the illustrated embodiment, the chip-scale LIDAR sensor 21 also includes a coupler 34, such as a 2x2 coupler, i.e., a 50:50 2x2 coupler. During operation, the coupler 34 is configured to optically combine, e.g., mix, radiation received by the input coupler 32, such as radiation scattered from the blade 14, with a second portion 31 b of the radiation, i.e., the LO beam generated by the laser source 22, and split the combination equally to each of the photodetectors 26 a and 26 b. The coupler 34 of the exemplary embodiment may be a directional or MMI coupler. In the illustrated embodiment, the coupler 34 provides the combined radiation to a pair of dual balanced photodetectors 26a and 26b.

[0024] 2, multiple components of the chip-scale LIDAR sensor 21 may be connected by a waveguide 36, such as an integrated photonic waveguide, e.g., a network of silicon-based waveguides. In the illustrated embodiment, the waveguide network includes a first waveguide 36a configured to guide radiation generated by the laser source 22 to the splitter 30, a second waveguide 36b configured to guide a second portion 31b of the radiation from the splitter to the coupler 34, and a third waveguide 36c configured to guide a first portion 31a of the radiation from the splitter to the output coupler 28. The waveguide network of the illustrated embodiment may also include a fourth waveguide 36d configured to guide received radiation from the input coupler 32 to the coupler 34, as well as fifth and sixth waveguides 36e and 36f configured to guide portions of the radiation received from the coupler to a pair of balanced photodetectors 26a and 26b, respectively. The waveguide 36 may be integrated with the substrate and may exhibit relatively low loss, such as less than 4 dB / cm. In this regard, light generated by the laser source 22 may be coupled into the first waveguide 36a by a spatial mode converter 24 that matches a larger optical spatial mode of the laser source 22 to a smaller mode of the first waveguide.

[0025] 3 , track sensor 20, such as chip-scale LIDAR sensor 21, is a component of blade positioning system 40, which also includes processing circuitry 42. In operation, blade positioning system 40 is configured to dynamically measure blade positions during flight of rotorcraft 10. In some embodiments, blade positioning system 40 is also configured to reposition blades 14 based on the dynamic measurements of blade positions during flight of rotorcraft 10.

[0026] The processing circuitry 42 of the blade positioning system 40 responds to the track sensor 20, such as signals captured by at least one photodetector 26 of the chip-scale LIDAR sensor 21, to determine blade position and / or altitude of the rotorcraft 10. The processing circuitry 42 may be embodied in several different ways, for example, it may include one or more processing units configured to execute independently. Additionally or alternatively, the processing circuitry 42 may include one or more processors configured in tandem via a bus to enable independent execution of software instructions, pipelines, and / or multiple threads. Use of the terms "processor" or "processing circuitry" may be understood to include a single-core processor, a multi-core processor, multiple processors, remote or "cloud" processors, or any combination thereof.

[0027] In one example, processing circuitry 42 may include one or more dedicated processors, controllers, specially configured field programmable gate arrays (FPGAs), or application-specific interface circuits (ASICs) to perform the corresponding functions. Processing circuitry 42 may also or instead be implemented using a processor executing software stored on a memory device. Thus, in this manner, processing circuitry 42 may be implemented using dedicated components implemented purely through hardware design, or may utilize hardware components executing computer software designed to facilitate the performance of the processing circuit's functions.

[0028] Processing circuitry 42 may also include or be associated with a memory device, and the processing circuitry in this example may be configured to execute software instructions stored on or otherwise accessible to the memory device. In this example, the memory device may be configured to store information, data, content, applications, software instructions, etc., to enable processing circuitry 42 to perform various functions in accordance with the examples contemplated herein. Alternatively, or in addition, processing circuitry 42 may be configured to execute hard-coded functions. Thus, whether configured in a hardware or software manner or a combination of hardware and software, processing circuitry 42, while configured accordingly, may represent an entity (e.g., physically embodied in circuitry) capable of performing operations in accordance with examples of the present disclosure. Alternatively, as another example, if processing circuitry 42 is embodied as an executor of software instructions, the software instructions may specifically configure the circuitry to perform the algorithms and / or operations described herein when the software instructions are executed.

[0029] Operations performed by blade positioning system 40, such as that of FIG. 3, to dynamically measure blade position during flight of rotorcraft 10 according to an exemplary embodiment are illustrated in FIG. 4. As indicated by block 50 of FIG. 4, blades 14 of rotorcraft 10 are repeatedly illuminated during flight of the rotorcraft while the blades rotate. In this regard, laser source 22 of track sensor 20 is configured to generate radiation, e.g., light, that repeatedly illuminates rotating blades 14 of rotorcraft 10. For example, as shown in FIG. 1, track sensor 20 is preferably mounted on top surface 13 of rotorcraft fuselage 12 such that track sensor 20 is below the rotational path of multiple blades 14, such that the blades extend radially beyond the track sensor and pass the track sensor during their rotation. Track sensor 20 of this exemplary embodiment is positioned to direct radiation generated by laser source 22 upward toward multiple blades 14 that pass the track sensor during their rotation, as indicated by the dashed lines in FIG. 1.

[0030] A track sensor 20, such as a laser source 22, may be configured to repeatedly illuminate the blade 14 of the rotorcraft 10 during its rotation by generating periodic pulses of radiation, e.g., laser pulses. Depending on the frequency at which the pulses are generated, the track sensor 20 may be configured to separately illuminate the blade 14 multiple times during a single blade pass over the track sensor. Alternatively, the track sensor 20 may be configured to illuminate the blade 14 during each rotation of the blade over the track sensor. In either case, the track sensor 20 is configured to repeatedly illuminate the blade 14 as it rotates.

[0031] As shown in block 52 of Figure 4, radiation scattered from blade 14 in response to illumination of the blade by laser source 22 is detected by at least one photodetector 26. As shown in Figure 6, preferably, the underside of blade 14 facing fuselage 12 of rotorcraft 10 may be illuminated by radiation generated by laser source 22. Radiation scattered by blade 14 in response to illumination is then detected by at least one photodetector 26.

[0032] Although the blade positioning system 40 is described as including a single track sensor 20, the blade positioning system of the exemplary embodiment may include multiple track sensors 20a, 20b, and 20c, each configured to separately illuminate the blade 14 and receive radiation scattered from the blade in response to the illumination. While the multiple track sensors 20 can be mounted to the fuselage 12 of the rotorcraft 10 in a variety of ways, FIG. 5 illustrates multiple track sensors including a first track sensor 20a, shown in solid lines, and multiple additional track sensors 20b and 20c, shown in dashed lines, angularly and / or radially offset to form the first track sensor. By separately determining blade position based on radiation scattered from the blade 14 and detected by the multiple track sensors 20, the accuracy with which the blade position is determined may be improved based on a combination, such as averaging, of the blade positions determined by each of the multiple track sensors. Furthermore, incorporating multiple track sensors 20 improves redundancy, thereby improving the reliability of the blade positioning system 40.

[0033] As shown in FIG. 6 , in accordance with an exemplary embodiment, blade 14 is repeatedly illuminated at a location 19 that is closer to the distal end 18 of the blade than rotor mast 16 about which the blade rotates. In this regard, track sensor 20 may be mounted on fuselage 12 at a location (indicated by dashed line 14a in FIG. 5 ) below the path of rotation of blade 14 but closer to the periphery or circumference of the path of rotation than rotor mast 16. In this regard, location 19 at which blade 14 is illuminated may be spaced a distance d1 from distal end 18 of blade 14 and may be spaced a distance d2 from rotor mast 16. Because location 19 at which blade 14 is illuminated is closer to distal end 18 of blade 14 than rotor mast 16, distance d1 is less than distance d2. The exemplary embodiment method and blade positioning system 40 can more precisely and accurately determine blade position by repeatedly illuminating the blade 14 at a location 19 closer to the blade's distal end 18 than to the rotor mast 16, because at least some variations in blade position are more pronounced near the blade's distal end than near the rotor mast.

[0034] As shown in block 54 of FIG. 4 , at least one of the blade pitch angle, blade flap angle, blade lead position, or blade lag position is determined, such as by the processing circuitry 42, based on radiation scattered from the blade 14 and detected, such as by at least one photodetector 26 of the track sensor 20. As described below, the blade pitch angle and blade flap angle are determined, at least in part, based on a range to the blade 14. The range to the blade 14 defines a distance between the chip-scale LIDAR sensor 21 and the illuminated portion of the blade 14. In this regard, the range may define either the distance between the chip-scale LIDAR sensor 21 and the illuminated portion of the blade 14, or the round-trip distance traveled by radiation between the chip-scale LIDAR sensor 21 and the illuminated portion of the blade 14. As shown in block 60 of FIGS. 7 and 8 , the processing circuitry 42 is configured to determine a range to the blade 14 based on radiation generated by the laser source 22, scattered from the blade, and then detected by the at least one photodetector 26. For example, processing circuitry 42 may be configured to determine the range to blade 14 based on the optical frequency shift between the transmission of radiation produced by FMCW laser source 22 and the detection of scattered radiation therefrom.

[0035] With respect to the blade pitch angle, processing circuitry 42 of the exemplary embodiment also calculates the width W of blade 14. Band determining a blade pitch angle based on a deviation of the range to the blade relative to a range to a no-pitch reference blade position, such as the position of a flat blade that would be located along horizontal axis 56 in the exemplary embodiment of FIG. 7 . See block 62 in FIG. 8 . The width of the blade 14 may be predefined, and in some embodiments, the range to the no-pitch reference blade position may also be predefined. However, in other embodiments, the range to the no-pitch reference blade position may be defined by the range to the blade 14 at the blade central axis 14 a, i.e., an axis extending radially outward from the rotor mast 16 to the distal end 18 of the blade and located widthwise at the center of the blade. Thus, the track sensor 20 of the exemplary embodiment may be configured to repeatedly illuminate the blade 14, including illuminating the blade at the blade central axis 14 a and illuminating the blade at another location laterally offset from the blade central axis. As shown in FIG. 7 and in this exemplary embodiment, the track sensor 20 can be configured to illuminate the blade 14 at the lateral edge 14 b of the blade so that the range determination, and consequently the range deviation determination, can be based on the range at the lateral edge of the blade.

[0036] In the exemplary embodiment shown in FIG. 7, processing circuitry 42 calculates the blade pitch angle Δθ according to the following relationship: P is configured to determine

number

[0037] In one example, the width of the blade 14 is 533 millimeters, and the blade pitch angle is expected to vary within a range of +6 degrees to -6 degrees from the blade flat position, for a total angular range of potential blade pitch angles of 12 degrees. In an embodiment where the blade pitch angle resolution is 0.1 degrees for a total of 120 resolved blade pitch angle positions, the resolution at which the range deviation is determined is 0.5 millimeters. The range deviation ΔR P This resolution for the determination of τ in turn depends on the degree of optical frequency modulation Δf and is defined as follows:

number

[0038] With respect to determining the blade flap angle, and with reference to block 70 of FIGS. 9 and 10 , processing circuitry 42 is configured to determine the range to blade 14 based on the detected radiation scattered from the blade, as described above in connection with determining the blade pitch angle. Processing circuitry 42 of this exemplary embodiment is also configured to determine the blade flap angle based on the length of blade 14 and the deviation of the range to the blade relative to a no-flap reference blade position, such as the no-flap blade position that would be located along horizontal axis 90 in the exemplary embodiment of FIG. 7 . See block 72 of FIG. 10 . The range to the no-flap reference blade position may be predefined or may be determined by track sensor 20 and processing circuitry 42 when the blade position is confirmed to be no-flap. In the exemplary embodiment, processing circuitry 42 determines the blade flap angle Δθ based on: F is configured to determine

number

[0039] In an exemplary embodiment in which the blade length is 7468 millimeters, the flap angle is expected to vary from +1 degree to -1 degree from the blade flat position, for a total range of 2 degrees of blade flap angle. In this exemplary embodiment, the blade positioning system 40 and method may be configured to determine the blade flap angle with a resolution of 0.1 degree, for a total of 20 resolved blade flap angle positions, etc. In this exemplary embodiment, the processing circuitry 42 is configured to determine the range to the blade 14 with a resolution of approximately 6.5 millimeters, such that the laser source 22 of the track sensor 20 in this exemplary embodiment provides an optical frequency modulation of approximately 23 GHz with a ramp waveform.

[0040] In another exemplary embodiment, processing circuitry 42 is configured to determine a blade position, such as a blade leading position or a blade lagging position, by determining the presence of a blade 14 at a predetermined position, i.e., a predetermined angular position, within the blade's rotational path and determining the detection time when the presence of the blade is detected. See blocks 80 and 82 in FIG. 11 . The blade leading position and blade lagging position are relative to a blade 14 that is angularly positioned relative to the rotor mast 16. A blade 14 in the blade leading position angularly leads the direction of rotation, while a blade in the blade lagging position angularly lags the direction of rotation. For a rotorcraft 10 having three blades 14, the blades can be properly angularly positioned when the blades are 120° apart. In this example, a blade 14 has a blade leading position when the rotational angle defined between the blade and a properly positioned leading blade is less than 120°. Conversely, a blade has a blade lagging position when the rotational angle defined between the blade and a properly positioned trailing blade is less than 120°.

[0041] Further, the presence of a blade 14 is defined as the detection by the chip-scale LIDAR sensor 21 of radiation scattered by the blade. In this regard, the multiple blades 14 rotate above the chip-scale LIDAR sensor 21. For each blade 14, the radiation generated by the chip-scale LIDAR sensor 21 generally does not impinge on and is not scattered by the respective blade because the respective blade does not cover the chip-scale LIDAR sensor and is not illuminated by the radiation generated thereby. However, for a small portion of the time required for the blade 14 to complete a single rotation around the rotor mast 16, the respective blade covers the chip-scale LIDAR sensor 21 and is illuminated by and scatters the radiation generated by the chip-scale LIDAR sensor. Upon detecting the radiation scattered by each blade 14, the chip-scale LIDAR sensor 21 detects the presence of the respective blade. In this regard, the processing circuitry 42 identifies the time when the leading edge of the blade 14 (or the trailing edge of the blade) is detected based on the scattered radiation detected by the track sensor 20, thereby determining the time when the respective edge of the blade is detected. For a properly positioned blade 14 with no lead or lag, the time at which the blade is detected by the track sensor 20 can be predetermined based on the blade's rotational speed, the blade's initial position, and so on.

[0042] In this exemplary embodiment, processing circuitry 42 is configured to determine the blade position based on a relationship between the detection time and a predetermined time at which a properly positioned blade, neither leading nor lagging, would have been detected. See block 84 of FIG. 11 . In this regard, processing circuitry 42 is configured to determine the blade position by determining that blade 14 is leading if the detection time leads the predetermined time, i.e., if blade positioning system 40 detects the presence of a blade before the time at which the blade positioning system is expected to detect the presence of a properly positioned blade. Processing circuitry 42 in this exemplary embodiment is also configured to determine that blade 14 is lagging if the detection time follows the predetermined time, such as when blade positioning system 40 detects the presence of a blade after the predetermined time at which the blade positioning system is expected to detect the presence of a properly positioned blade. Based on the difference between the detection time and the predetermined time, blade positioning system 40 is configured not only to determine whether blade 14 is leading or lagging, but also to determine the angular amount by which the blade is leading or lagging based on the rotational speed of the blade and the difference between the detection time and the predetermined time.

[0043] As shown in FIG. 3 , the blade positioning system 40 of the exemplary embodiment also includes one or more actuators 44. In this exemplary embodiment, the one or more actuators are responsive to the processing circuitry 42 and configured to modify the position of the blade 14 during flight based on the determined blade position. For example, the blade positioning system 40 may include a blade pitch actuator 44a configured to modify the blade pitch based on the determined blade pitch angle so that the blade 14 can be returned to a flat position during flight. Similarly, the blade positioning system 40 may include a blade flap actuator 44b configured to modify the blade flap based on the determined blade flap angle so that the blade 14 can be returned to a flat position during flight. Furthermore, the blade positioning system 40 may include a blade angle position actuator 44c configured to modify the blade position, such as the blade angle position, based on a determination as to whether the blade 14 is leading or lagging, so that the blade can be returned to a desired angular position that is neither leading nor lagging. Thus, a blade positioning system 40, such as at least one actuator 44, is configured to controllably modify the position of the blade 14 during flight to offset blade position variations and return the blade to a desired position, thereby improving flight conditions, such as by providing a smoother flight without waiting for the completion of the flight and / or for the rotorcraft to return to a maintenance depot or other facility where necessary repairs can be performed.

[0044] The radiation produced by the laser source 22 illuminates the blade 14 and has a finite dwell time T B and the residence time is determined by the blade rotation speed υ R and depends on the position of the track sensor 20 relative to the axis about which the blade rotates, for example defined as the radius R from the axis about which the blade rotates to the track sensor, and is defined as follows:

number

[0045] For the example blade 14 having the above dimensions, if the track sensor is positioned closer to the distal end 18 of the blade than the rotor mast 16, the minimum dwell time of radiation generated by the track sensor 20 on the blade 14 is approximately 5 milliseconds for a blade rotating at a speed of 258 revolutions per minute (RPM). In an embodiment in which the beam size of the radiation generated by the laser source 22 of the track sensor 20 is approximately 3 millimeters, the spot size of the radiation on the blade 14 3 meters away from the track sensor is approximately 7 millimeters. In this exemplary embodiment, a single track sensor 20 generates approximately 78 measurement points across the width of the blade 14 (two of which are indicated by dots 15 in FIG. 5 ) during a single rotation with a measurement time (or integration time) of approximately 64 microseconds for each measurement. In this regard, the measurement time is the dedicated time following illumination of the blade 14 for radiation to scatter from the blade and subsequently be detected by at least one photodetector 26 of the track sensor 20. In embodiments where it is desired to measure range with increased accuracy or resolution, the measurement time, or integration time, for each measurement point is increased, thereby reducing the number of measurement points across the width of the blade 14. For example, if the measurement time, or integration time, is increased to approximately 5 milliseconds, the track sensor 20 may be configured to generate five measurement points across the width of the blade 14.

[0046] As described above, the chip-scale LIDAR sensor 21 can be utilized to determine blade position, thereby enabling blade position correction during flight in a controlled manner. Alternatively, the chip-scale LIDAR sensor 21 may be utilized as, or in combination with, an altimeter to determine the altitude of the rotorcraft 10 above a surface, such as during landing of the rotorcraft. In this exemplary embodiment, as shown in FIG. 12 , an altitude sensor 100 including the chip-scale LIDAR sensor 21 may be mounted on the underside 102 of the fuselage 12 of the rotorcraft 10 and configured to illuminate a surface 104 below the rotorcraft, such as the terrain on which the rotorcraft will land, as indicated by the downwardly diverging dashed lines. Based on the optical frequency shift between the generation of radiation by the laser source 22 of the chip-scale LIDAR sensor 21 and the detection of radiation scattered by the underlying terrain by at least one photodetector 26 in response to illumination by the radiation, the range to the underlying terrain, such as the altitude of the rotorcraft 10, can be determined by the processing circuitry 42 or the like. Thus, rotorcraft 10 may be maneuvered relative to the underlying terrain in a controlled manner, such as by landing the rotorcraft on the terrain.

[0047] 4, 8, 10, and 11 illustrate flowcharts illustrating the operation of apparatuses, methods, and computer program products according to examples of the present disclosure. It is understood that each block of the flowcharts, and combinations of blocks within the flowcharts, may be implemented by various means embodied in hardware, firmware, circuitry, and / or other devices associated with the execution of software including one or more software instructions. For example, one or more of the operations described above may be embodied in software instructions. In this regard, software instructions embodying the above procedures may be stored by a memory of a blade positioning system 40 using examples of the present disclosure and executed by the processing circuitry 42 of a computing device. As will be appreciated, such software instructions may be loaded into a computer or other programmable device (e.g., hardware) to generate a machine, causing the resulting computer or other programmable device to perform the functions specified in the flowchart blocks. These software instructions may also be stored in a computer-readable memory that can instruct the computer or other programmable device to function in a particular manner, such that the software instructions stored in the computer-readable memory generate a product that executes to perform the functions specified in the flowchart blocks. The software instructions can also be loaded into a computer or other programmable device to perform a sequence of operations on the computer or other programmable device, creating a computer-implemented process such that the software instructions executing on the computer or other programmable device provide operations to perform the functions specified in the flowchart blocks.

[0048] The flowchart blocks support a combination of means for performing a specified function and a combination of operations for performing a specified function. It will be understood that one or more blocks of the flowcharts, and combinations of blocks within the flowcharts, can be realized by a dedicated hardware-based computer system that performs the particular function, or a combination of dedicated hardware and software instructions.

[0049] In some examples, some of the above operations may be modified or further amplified. Furthermore, in some examples, additional optional operations may be included. The modifications, amplifications, or additions of the above operations may be performed in any order and in any combination.

[0050] Furthermore, the present disclosure includes embodiments according to the following clauses:

[0051] Clause 1. A method for dynamically measuring blade position during flight of a rotorcraft, comprising: repeatedly illuminating a rotorcraft blade with coherent light while the rotorcraft blade is rotating; detecting radiation scattered from the blade in response to illuminating the blade; and determining at least one of a blade pitch angle, a blade flap angle, a blade leading position, or a blade lagging position based on the detected radiation scattered from the blades.

[0052] Clause 2. The method of clause 1, wherein the step of repeatedly illuminating a blade of a rotorcraft includes the step of repeatedly illuminating the blade at a location closer to a distal end of the blade than a rotor mast about which the blade rotates.

[0053] Clause 3. The method of clause 1, wherein the step of repeatedly illuminating a blade of the rotorcraft includes the step of repeatedly illuminating the blade with a plurality of track sensors positioned at different locations on a fuselage of the rotorcraft.

[0054] Clause 4. The step of determining the blade pitch angle comprises: determining a range to the blade based on the detected radiation scattered from the blade; determining a blade pitch angle based on the width of the blade and the deviation of the range to the blade from a no-pitch reference blade position.

[0055] Clause 5. The method of clause 4, wherein the step of repeatedly illuminating the blade includes the step of repeatedly illuminating the blade with radiation generated by a laser source, and the step of determining the range includes the step of determining the range between the laser source and the edge of the blade.

[0056] Clause 6. The step of determining the blade flap angle comprises: determining a range to the blade based on the detected radiation scattered from the blade; determining a blade flap angle based on the length of the blade and the deviation of the range to the blade from the range to a reference blade position without the flap.

[0057] Clause 7. The step of determining a blade advance position or a blade lag position comprises: detecting the presence of the blade at a predetermined position within the blade's rotational path; determining a detection time at which the presence of a blade is detected; The method of claim 1, including a step of determining a blade position based on a relationship between the detection time and a predetermined time associated with a reference blade that is neither advanced nor delayed, wherein the step of determining the blade position includes a step of determining a blade advanced position when the detection time precedes the predetermined time, and a step of determining a blade delayed position when the detection time lags the predetermined time.

[0058] Clause 8. A blade positioning system for dynamically measuring blade position during flight of a rotorcraft, the blade positioning system comprising: 1. A track sensor mounted on a rotorcraft, comprising: a laser source that repeatedly illuminates a blade of the rotorcraft with coherent light while the blade is rotating during flight of the rotorcraft; a track sensor including at least one photodetector that detects radiation scattered from the blade in response to illumination of the blade; and processing circuitry responsive to the track sensor to determine at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on radiation scattered from the blades and detected by the at least one photodetector.

[0059] Clause 9. The blade positioning system of clause 8, wherein the track sensor is mounted to the rotorcraft such that the laser source is configured to repeatedly illuminate the blade at a location closer to a distal end of the blade than a rotor mast about which the blade rotates.

[0060] Clause 10. The blade positioning system of clause 8, further comprising a plurality of track sensors mounted at different locations on the rotorcraft.

[0061] Clause 11. The processing circuitry configured to determine the blade pitch angle comprises: determining a range to the blade based on the detected radiation scattered from the blade; 9. The blade positioning system of claim 8, including processing circuitry configured to determine a blade pitch angle based on a deviation of a range to the blade relative to a width of the blade and a range to a reference blade position without pitch.

[0062] Clause 12. The blade positioning system of clause 11, wherein the processing circuitry configured to determine the range includes processing circuitry configured to determine the range between the laser source and the edge of the blade.

[0063] Clause 13. The processing circuit configured to determine the blade flap angle comprises: determining a range to the blade based on the detected radiation scattered from the blade; 9. The blade positioning system of claim 8, including processing circuitry configured to determine a blade flap angle based on a length of the blade and a deviation of a range to the blade relative to a no-flap reference blade position.

[0064] Clause 14. The track sensor is configured to detect the presence of the blade at a predetermined position within the blade's rotational path, and the processing circuitry configured to determine a blade leading position or a blade lagging position comprises: determining a detection time at which the presence of the blade was detected; 9. A blade positioning system as described in clause 8, including a processing circuit configured to determine a blade position based on a relationship between the detection time and a predetermined time associated with a reference blade that is neither advanced nor delayed, wherein the processing circuit configured to determine the blade position includes processing circuitry configured to determine a blade advanced position when the detection time advances the predetermined time and to determine a blade delayed position when the detection time lags the predetermined time.

[0065] Article 15. Rotorcraft: The torso and a plurality of blades that rotate relative to the fuselage; Mounted on the fuselage, a laser source for providing illumination with coherent light during flight of the rotorcraft; at least one photodetector that detects scattered radiation in response to illumination provided by the laser source; and a chip-scale light detection and ranging (LIDAR) sensor that includes: A chip-scale LIDAR sensor may be carried by the fuselage of a rotorcraft, with a laser source configured to illuminate multiple blades while they are rotating, either to allow the position of the blades to be measured or to illuminate the terrain below the rotorcraft to provide altimetry.

[0066] Clause 16. The rotorcraft of clause 15, wherein the laser source comprises a frequency modulated continuous wave laser diode.

[0067] Clause 17. The rotorcraft of clause 15, wherein the at least one photodetector includes a pair of dual balanced photodetectors.

[0068] Article 18. Chip-scale LIDAR sensors are a splitter that divides light generated by the laser source into first and second portions, the first portion being directed to illuminate the blades while the blades are rotating or to illuminate terrain beneath the rotorcraft; and a waveguide that supports propagation of a second portion of the light generated by the laser source; a coupler that combines a second portion of the light propagating along the waveguide with radiation scattered in response to illumination provided by the laser source; 16. The rotorcraft of clause 15, wherein the at least one optical detector is configured, in response to the coupler, to receive a second portion of the light propagating along the waveguide along with radiation scattered in response to illumination provided by the laser source from the coupler.

[0069] Clause 19. The rotorcraft of clause 15, further comprising processing circuitry responsive to the chip-scale LIDAR sensor to determine at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on radiation scattered from each blade of the plurality of blades and detected by the at least one photodetector.

[0070] Clause 20. The rotorcraft of clause 19, further including an actuator responsive to the processing circuitry to modify a position of each blade during flight based on at least one of a blade pitch angle, a blade flap angle, a blade advance position, or a blade retard position determined by the processing circuitry.

[0071] Many modifications and other examples of the disclosure described herein will come to mind to those skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Accordingly, it should be understood that the disclosure is not limited to the particular examples disclosed, and that modifications and other examples are intended to be included within the scope of the appended claims. Furthermore, while the foregoing description and the associated drawings describe examples in the context of particular combinations of elements and / or functions, it should be understood that different combinations of elements and / or functions may be provided by alternative examples without departing from the scope of the appended claims. In this regard, combinations of elements and / or functions other than those expressly described above are also contemplated, for example, as set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. [Explanation of symbols]

[0072] 10. Rotorcraft 12 Torso 13 Top side 14 blades 14a Blade center axis 14b lateral edge 15 dots 16 Rotamast 18 distal end 19 position 20 Track Sensor 20a Truck Sensor 20b Truck Sensor 20c Truck Sensor 21 Chip-scale LIDAR sensor 22 Laser Source 24 Spatial mode converter 26 Photodetector 26a Dual Balanced Photodetector 26b Dual Balanced Photodetector 28 Output Coupler 30 Splitter 31a First Section 31b Second part 32 Input Coupler 34 Coupler 36 Waveguide 36a First waveguide 36b Second waveguide 36c Third waveguide 36d Fourth Waveguide 36e Fifth Waveguide 36f 6th waveguide 40 Blade Positioning System 42 Processing circuit 44 Actuator 44a Blade Pitch Actuator 44b Blade flap actuator 44c Blade angle position actuator 56 horizontal axis 90 horizontal axis 100 Altitude Sensor 102 Bottom surface 104 Ground surface

Claims

1. A rotorcraft, comprising: The torso and a plurality of blades that rotate relative to the fuselage; a fuselage-mounted chip-scale light detection and ranging (LIDAR) sensor; a laser source for providing illumination with coherent light during flight of the rotorcraft; at least one photodetector that detects scattered radiation in response to illumination provided by the laser source; a chip-scale light detection and ranging (LIDAR) sensor including: Including, the chip-scale LIDAR sensor is carried by the fuselage such that the laser source is configured to illuminate the plurality of blades while the blades are rotating to enable the positions of the blades to be measured or to illuminate terrain below the rotorcraft to provide altitude measurements.

2. A rotorcraft as described in claim 1, wherein the laser source includes a frequency modulated continuous wave laser diode.

3. A rotorcraft as described in claim 1, wherein the at least one optical detector includes a pair of dual balanced optical detectors.

4. The chip-scale LIDAR sensor comprises: a splitter that divides light generated by the laser source into first and second portions, the first portion being directed to illuminate the plurality of blades while the blades are rotating or to illuminate terrain beneath the rotorcraft; and a waveguide that supports propagation of the second portion of light generated by the laser source; a coupler that combines the second portion of light propagating along the waveguide with radiation scattered in response to illumination provided by the laser source; 2. The rotorcraft of claim 1, wherein the at least one optical detector is configured, in response to the coupler, to receive the second portion of light propagating along the waveguide along with radiation scattered in response to illumination provided by the laser source from the coupler.

5. The rotorcraft of claim 1, further comprising processing circuitry that, in response to the chip-scale LIDAR sensor, determines at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on radiation scattered from each blade of the plurality of blades and detected by the at least one optical detector.

6. A rotorcraft as described in claim 5, further comprising an actuator that, in response to the processing circuit, corrects the position of each blade during flight based on at least one of the blade pitch angle, the blade flap angle, the blade advance position, or the blade retard position determined by the processing circuit.

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